Department of Chemistry and Applied Biosciences, Institute for Chemical- and Bioengineering, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland.
Langmuir. 2010 May 18;26(10):7062-71. doi: 10.1021/la904390h.
The characterization of complex colloidal dispersions is a relevant and challenging problem in colloidal science. In this work, we show how asymmetric flow-field flow fractionation (AF4) coupled to static light scattering can be used for this purpose. As an example of complex colloidal dispersions, we have chosen two systems undergoing aggregation. The first one is a conventional polystyrene latex undergoing reaction-limited aggregation, which leads to the formation of fractal clusters with well-known structure. The second one is a dispersion of elastomeric colloidal particles made of a polymer with a low glass transition temperature, which undergoes coalescence upon aggregation. Samples are withdrawn during aggregation at fixed times, fractionated with AF4 using a two-angle static light scattering unit as a detector. We have shown that from the analysis of the ratio between the intensities of the scattered light at the two angles the cluster size distribution can be recovered, without any need for calibration based on standard elution times, provided that the geometry and scattering properties of particles and clusters are known. The nonfractionated samples have been characterized also by conventional static and dynamic light scattering to determine their average radius of gyration and hydrodynamic radius. The size distribution of coalescing particles has been investigated also through image analysis of cryo-scanning electron microscopy (SEM) pictures. The average radius of gyration and the average hydrodynamic radius of the nonfractionated samples have been calculated and successfully compared to the values obtained from the size distributions measured by AF4. In addition, the data obtained are also in good agreement with calculations made with population balance equations.
复杂胶体分散体的特性是胶体科学中的一个重要且具有挑战性的问题。在这项工作中,我们展示了如何将不对称流场分级(AF4)与静态光散射相结合来实现这一目的。作为复杂胶体分散体的一个例子,我们选择了两个发生聚集的体系。第一个是传统的聚苯乙烯乳胶,它经历了反应限制聚集,导致具有已知结构的分形团簇的形成。第二个是由玻璃化转变温度低的聚合物制成的弹性胶体颗粒的分散体,在聚集时发生聚结。在聚集过程中,我们在固定时间点取出样品,并用 AF4 进行分级,使用双角度静态光散射单元作为检测器。我们已经表明,通过分析两个角度的散射光强度比,可以恢复簇大小分布,而无需基于标准洗脱时间的校准,前提是颗粒和簇的几何形状和散射特性已知。我们还通过常规静态和动态光散射对非分级样品进行了表征,以确定它们的转动半径和流体力学半径。通过对冷冻扫描电子显微镜(SEM)图像的图像分析,也研究了聚结颗粒的大小分布。还计算了非分级样品的转动半径平均值和流体力学半径平均值,并成功地与通过 AF4 测量的尺寸分布得到的值进行了比较。此外,所得到的数据还与用群体平衡方程进行的计算吻合得很好。
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